add bb prereqs to documentation

docs/d_prerequisites.md

+# Appendix D - Big Bang Prerequisites
+
+BigBang is built to work on all the major kubernetes distributions.  However, since distributions differ and may come
+configured out the box with settings incompatible with BigBang, this document serves as a checklist of pre-requisites
+for any distribution that may need it.
+
+## All Clusters
+
+The following apply as prerequisites for all clusters
+
+* A default `StorageClass` capable of resolving `ReadWriteOnce` `PersistentVolumeClaims` must exist